The present invention relates in general to intraluminal medical devices, and more particularly to guide wire tips.
The use of intraluminal catheters for treatment of various medical problems within the body is well known. It is also well known that a variety of difficulties may be encountered as the catheter is steered through the selected lumen to a desired point within the body. The path may be tortuous and the point of interest may be difficult to locate precisely. To overcome these difficulties, a flexible guide wire may first be inserted into the vascular lumen to the desired location. Once a guide wire is in position, a desired catheter may then be slid over the guide wire to reach the desired situs in the body.
It can readily be seen that it is important to have a guide wire that is flexible enough to traverse the tortuous vascular system. It can also be readily seen that it is important to-have a guide wire that is radioscopic such that the physician can verify the position or location of the guide wire within the vascular lumen.
A continuing series of technical improvements and additions have been made in the catheter field to provide devices and methods which can overcome certain of these difficulties. One such series of improvements has resulted in the now well known use of a thin flexible guide wire having a tapered distal section that can be more easily steered through the lumen by forces applied to a proximal section. Because the distal section of a tapered guide wire may lose pushability, another improvement that has been developed is the use of a coiled wire helix which is wrapped around the distal tapered section of the guide wire. The coiled wire helix may improve the pushability of the distal tapered section of the guide wire while maintaining overall flexibility.
An example of a guide wire having a coiled wire helix is disclosed in U.S. Pat. No. 4,619,274 issued to Morrison. Morrison discloses a core member having a proximal and a distal end wherein the core member has a decreasing cross sectional area in a direction toward the distal end. The decreasing cross sectional area is incremental in that the core member comprises a plurality of fixed diameter cylinders which are coupled together by tapered sections. The diameters of the fixed diameter cylinders become smaller in the direction of the distal end of the core member.
Morrison further discloses a tapered coil which is carried and secured to the core element and extends over the core element. The tapered coil has a proximal end and a distal end wherein the diameter of the tapered coil-decreases toward the distal end. Furthermore, the coil is formed of wire having a diameter which decreases toward the distal end. The improvements suggested by Morrison may provide some increased pushability while maintaining a degree of flexibility. However, the decreasing diameter core member and tapered coil may limit the pushability of the distal tip of the core member.
Another example of a guide wire having a coiled wire helix is disclosed in U.S. Pat. No. 4,846,186 issued to Box et al. In Box et al., a core member having an initial uniform diameter segment tapers along a uniform portion to a second constant diameter segment. A flexible spring tip surrounds, and is attached to, the second constant diameter segment and extends distally therefrom. The core member again tapers in a region where the flexible spring separates from the core member. Within the flexible spring, a portion of the core member is flattened to increase the flexibility of the distal portion of the core member. The flattened core and spring are brazed together at an extreme distal tip portion to form a distal guide wire tip.
A further variant of a guide wire having a reduced diameter distal portion surrounded by a coil wire helix is disclosed in U.S. Pat. No. 4,538,622 to Samson et al. The guide wire disclosed in Samson et al. includes an elongated stainless steel core wire having a reduced diameter distal portion including two constant diameter portions- and two tapered portions.
The reduced diameter distal portion is surrounded by a first proximately disposed coil and a second distally disposed coil. The proximate coil is preferably stainless steel and is soldered at its proximal end to the core wire. The distal coil is preferably formed from a radiopaque material such as gold or platinum to allow location of the distal end of the guide wire by fluoroscopy. Under a fluoroscope, the radiopaque coil will appear brightly.
The proximal end of the distal end coil is threaded into the distal end of the proximal coil. The coils are joined into a unitary assembly by brazing. The brazing also secures the coils to the core wire. The brazing however, fills the space between the coils and the wire over a length of the reduced diameter portion. This consequently increases the effective diameter of the core wire abruptly, thus changing the core wire""s flexibility at the braze or solder.
The present invention pertains generally to improved guide wire tips. These tips include various configurations of core wires, coils and radiopaque material to enhance their handling characteristics and visibility by reducing radioscopic means.
A guide wire tip in accordance with the preferred embodiment of the present invention includes a -core wire having a proximal end and a distal end. The core wire includes a tapered portion proximate the distal end. The tapered portion has a transverse, cross-sectional area which generally decreases distally. A tip is disposed at the distal end of the guide wire. The tip has a transverse, cross-sectional area larger than the smallest transverse cross-sectional area of the tapered portion of the core wire. A coil extends over the core wire to the tip and extends over at least a portion of the tapered portion. A radiopaque sheath is disposed proximate the tip and between the core wire and the coil.
The coil can be radiopaque and formed from a material such as platinum. The sheath is preferably a radiopaque loaded heat shrink tube. The tip is atraumatically rounded at its distal end. The tip and/or core wire can be formed from stainless steel. The core wire can include a portion having a circular transverse cross section and a portion having a ribbon shaped transverse cross section proximate its distal end. A transition between the circular cross section portion and the ribbon portion can have a generally parabolic shape.
In yet another embodiment of a guide wire tip in accordance with the present invention, the core wire and tip can be as described above. First and second coils extend over the core wire. The first coil being proximate the tip and the second coil being proximal the first coil. A spacer is disposed between the coils. A low friction sleeve is- disposed over at least a portion of the second coil.
At least one of the coils can be radiopaque. The sleeve preferably is formed from PTFE. The spacer can be generally radiotranslucent.